LFTs

Question 1

What is the function of the liver? (5)

Answer 1

1. Bile production
2. Synthesis of albumin, clotting factors, glucose
3. Glucose, fat metabolism
4. Defence against infection
5. Detoxification and excretion of bilirubin, ammonia, drugs

Question 2

Why is bile important for and how is it synthesised?

Answer 2

(1. ) Bile is important for the breakdown of fats into fatty acids, which can be taken into the body by the digestive tract.
(2. ) Bile is synthesised in liver and stored in the gallbladder, where it becomes more concentrated

Question 3

What is measured in LFT and what do they indicate?

Answer 3

(1. ) ALT, AST, ALP and GGT are used to distinguish between hepatocellular damage and cholestasis.
(a. ) ALT and AST usually elevated in liver damage
(b. ) elevated ALP and GGT usually indicates cholestasis.

(2.) Bilirubin, albumin and PT are used to assess the liver’s synthetic function.

Question 4

How can ALT, ALP, GGT levels indicate hepatocellular injury or cholestasis

Answer 4

1. ALT increase is larger than ALP’s increase suggests hepatocellular injury
2. ALP increase is larger than ALT’s increase AND a GGT rise suggests cholestasis.

Question 5

What does an isolated rise of ALP in absence of raised GGT indicate?

Answer 5

(1. ) Raised ALP in absence of raised GGT indicates NON-HEPATIC pathology.
(2. ) ALP is present in bone - where BONE BREAKDOWN can increase ALP.

(3. ) This could be due to:
(a. ) Bony metastases or primary bone tumours
(b. ) Vitamin D deficiency
(c. ) Recent bone fractures
(d. ) Renal osteodystrophy

Question 6

ALT and ALP are normal but pt is jaundice? What is this due to?

Answer 6

Pre-hepatic jaundice is due rise of bilirubin e.g. Gilbert’s syndrome, Haemolysis

(1. ) Unconjugated bilirubin (breakdown of haem/RBC) is processed by the liver into conjugated bilirubin where it is excreted into the bile.
(2. ) H/E excessive red cell breakdown can overwhelms the liver’s ability to conjugate bilirubin. The liver can only process so much bilirubin at once, so bilirubin overflows into bodily tissues
(3. ) This can cause an isolated rise in bilirubin is suggestive of a pre-hepatic cause of jaundice.

Question 7

What investigations can be used to assess synthetic liver function?

Answer 7

1. Serum bilirubin
2. Serum albumin
3. Prothrombin time (PT)
4. Serum blood glucose

Question 8

Describe breakdown and excretion of bilirubin

Answer 8

(1. ) Bilirubin is the breakdown of haemoglobin
(2. ) Unconjugated bilirubin is taken up by liver and is then conjugated.
(3. ) Unconjugated bilirubin is water-insoluble and so doesn’t affect colour of patient’s urine. Whereas conjugated bilirubin is water soluble and is excreted in the urine, giving it a dark colour (bilirubinuria)
(4. ) Conjugated bilirubin is also excreted into bile and enters the duodenum where urobilinogen is formed and then excreted in faeces.

Question 9

Why may a pt experience steatorrhea?

Answer 9

If bile and pancreatic lipases are unable to reach the bowel because of a blockage (obstructive post-hepatic pathology), fat is not able to be absorbed, resulting in stools appearing pale, bulky and more difficult to flush.

Question 10

Causes of conjugated hyperbilirubinaemia? (3)

Answer 10

(1. ) Hepatocellular injury
(a. ) liver cells damaged and can’t conjugate bilirubin anymore
(b. ) liver cells die and release their bilirubin
(2. ) Cholestasis
(3. ) OR extrahepatic obstruction that prevents bilirubin from moving into the intestines so instead more conjugated bilirubin enters the blood

Question 11

Causes of unconjugated hyperbilirubinaemia ? (4)

Answer 11

(1. ) Haemolysis, RBC lysis (e.g. haemolytic anaemia)
(2. ) Ineffective Hematopoesis - RBC do not form properly so are broken down by macrophages
(3. ) Impaired hepatic uptake (e.g. drugs, congestive cardiac failure)
(4. ) Impaired conjugation (e.g. Gilbert’s syndrome)

Question 12

In liver cirrhosis, what would you expect to see in albumin and glucose levels? and PT time?

Answer 12

• Dec albumin production
• Hypoglycaemia
• Inc PT time due to reduction of the synthesis of clotting factors

Question 13

Common causes of acute hepatocellular injury? (3)

Answer 13

• Poisoning (paracetamol overdose)
• Infection (Hepatitis A and B)
• Liver ischaemia

Question 14

Common (4) and less common (3) causes of chronic hepatocellular injury?

Answer 14

Common

• AFLD
• NAFLD
• Chronic infection (Hepatitis B or C)
• Primary biliary cirrhosis

Rare

• Alpha-1 antitrypsin deficiency
• Wilson’s disease
• Haemochromatosis

Question 15

What conditions causes an isolated raised Bilirubin in an otherwise healthy patient?

Answer 15

Gilbert’s syndrome

This is a genetic condition which causes you to have problems processing bilirubin.

Question 16

What does an isolated raised ALP indicate?

Answer 16

If ALP is raised but the rest of your LFTs are normal consider a condition that affects your BONES (might be a malignancy)

Check calcium and vitamin D levels.

ALP can also be raised in pregnancy as the placenta releases it.

Question 17

What LFT markers may indicate a pt is a heavy drinker?

Answer 17

(1. ) ALT
- If ALT is raised 2x more than your AST this indicates the patient is a heavy drinker (think about advising them to cut down).

(2. ) GGT
- GGT is also raised in 80% of people who drink alcohol (think about asking them to cut down)

Question 18

Pt with pancreatic tumour - what LFTs would you expect to see? Why may they present with painless jaundice?

Answer 18

(1. ) Raised GGT and ALP due to pancreatic tumour compressing onto biliary tree.
(2. ) Raised ALT and AST due to biliary tree obstruction could be causing a backlog of bile into the liver so hepatocytes are distressed
(3. ) Distressed hepatocytes aren’t processing bilirubin as they normally would, leading to increased bilirubin. Unconjugated bilirubin that remains in blood stream causes jaundice.

Question 19

Describe LFTs you’d see with a stone in the common bile duct that is causing (1.) Partial and (2.) Complete obstruction.

Answer 19

Partial Obstruction

• Flow of bile is not completely obstructed so GGT and ALP is raised.
• H/e liver is not affected so you would expect AST and ALT to be normal.

Complete Obstruction

• There is a backflow of bile into the liver due to the obstruction.
• Liver is not happy and neither are the bile ducts.
• Because of this, you may expect AST, ALT, GGT and ALP to all be raised.

Question 20

Describe LFTs you’d expect to see in Acute Hepatitis

Answer 20

• Raised AST, ALT
• GGT may be raised
• ALP is normal
• Hepatitis affects the liver so you would expect liver cells to not be very happy therefore AST and ALT will be raised.
• You would expect ALP to be normal as the bile ducts are unaffected.
• GGT may be raised as it is released from both the liver and bile ducts.

Question 21

Why may you get an increase in both unconjugated and conjugated bilirubin? And what would be seen as a result of this?

Answer 21

(1. ) Inc RBC breakdown
(2. ) Hepatic cells are working harder to make CB in response to the elevated UCB levels
(3. ) Liver can only work to a limit so high levels of UCB will be seen.
(4. ) Large amount of CB is being made and secreted this build up in bile can result in the formation of pigmented gallstones.
(5. ) Bile/CB is secreted into the gut and this inc levels of urobilinogen this is ultimately excreted by kidneys as darkens urine
(6. ) This can happen in viral hepatits.

Question 22

Conditions that causes inc conjugated bilirubin

Answer 22

(1.) Dublin-Johnson Syndrome - Liver cells can’t secrete CB into the bile canaliculus, but instead secrete CB into the blood so dark urine is seen

(2. ) Obstructive Jaundice
- Blockage of common duct due to gallstones, mirizzi, pancreatic and cholangio carcinoma, stricture
- Inc pressure of duct causes leakage of its content into the blood
- Bile salt and acids, cholesterol (content) in the blood causes pruritis, cholesterolemia, xanthoma, dark urine, steatorrhea

Question 23

Why may viral hepatitis cause an inc in both UCB and CB in blood?

Answer 23

(1. ) hepatocytes get infected and start to die off, they both lose the ability to:
(a. ) conjugate bilirubin, leading to excess UCB in the blood
(b. ) AND since they also line the bile ducts, when they die they let bile leak out into the blood, causing an increase in blood CB as well –> more CB excreted and darker urine